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PPM Sensitivity of 10 MHz OFDM Channels

PPM Sensitivity of 10 MHz OFDM Channels. Mark Webster Al Garrett. Overview. 15 PPM oscillators are more expensive than 20 PPM oscillators. 802.11a specs 20 PPM. For 10 MHz channels, the PPM frequency error impacts Acquisition performance Tracking performance

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PPM Sensitivity of 10 MHz OFDM Channels

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  1. PPM Sensitivity of 10 MHz OFDM Channels Mark Webster Al Garrett Mark Webster, GlobespanVirata

  2. Overview • 15 PPM oscillators are more expensive than 20 PPM oscillators. 802.11a specs 20 PPM. • For 10 MHz channels, the PPM frequency error impacts • Acquisition performance • Tracking performance • Acquisition was addressed in doc:IEEE802.11-03/454r0 • It was shown that a 20 PPM spec has no degradation on acquisition performance • This new submission addresses tracking performance Mark Webster, GlobespanVirata

  3. Overview (cont’d) • Typical radio impairments are used to simulate 64 QAM 27 Mbps PER performance versus PPM error • Phase noise • PA distortion (EVM limited) • Tx/Rx filtering • DC notching using a HPF • It is shown that at worst-case PPM error (not typical) with the most sensitive 10 MHz modulation with 64 QAM at 27 Mbps, 20 PPM degradation is only 0.25 dB beyond 15 PPM’s degradation Mark Webster, GlobespanVirata

  4. Worst-Case Frequency Errorfor 10 MHz OFDM Channels Set Frequency Error to Worst Case Equivalent Osc. Spec 0 PPM spec 10 PPM spec 15 PPM spec 20 PPM spec Mark Webster, GlobespanVirata

  5. Conclusion • This submission has shown that the extra cost of the 15 PPM oscillator can be avoided with a 20 PPM spec • The extra link degradation with a 20 PPM spec is small • About 0.25 dB • Using 20 PPM minimizes 802.11a design changes required to implement 10 MHz channels Mark Webster, GlobespanVirata

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